The invention relates generally to determination of vehicle location, and, in particular, to a system and method for accurately and timely determining location/distance information for vehicles on a route, including, for example, trains on their tracks.
A need presently exists in vehicular (i.e. train) asset management and control applications to provide accurate and timely distance information for vehicles along a route, such as, but not limited to, trains on their tracks. An automatic controller in a locomotive pacing application, for example, provides throttle (notch) and braking commands to a locomotive in order that the locomotive follow a pre-planned speed profile versus distance along the track. In such an application, it is necessary to know the real-time location of the locomotive along the track. A locomotive position sensor or location determination system is therefore required.
One of the critical components of an automatic train control system is a sensor or sensor system that can provide accurate real-time location of the train on the track. Such a system must display robustness to errors and disturbances that are likely to be encountered in the railroad environment in order to be safely deployed. Such a system, for example, must provide plausible position information even if the sensors employed become subject to transient errors or intermittent lapses.
One of two methods has been typically employed to provide a location determination system (LDS). The first is a “dead reckoning” method based on measured velocity, the latter derived from a measurement of the rotational rate of one or more wheels and the corresponding wheel diameter. Position is computed simply by integrating the speed measurement, starting from a known initial position value.
The second method is based on real-time measurement of geographic coordinates with a GPS sensor. The coordinates are compared to track coordinates in a track database, and an association is made to a specific point in the track database based on minimizing the distance between the measured geographic location (latitude and longitude) and locations in the track database. More specifically a Kalman filter has been employed in conjunction with orthogonal acceleration measurements, turn-rate measurements, and wheel-mounted tachometer information for tracking movement through turnouts (to determine track occupancy) and for estimating along-track position, but that does not take into consideration certain errors and disturbances such as, for example, cumulative distance errors that are likely to be encountered along the specific track.
Accordingly, there exists a need for a reliable system and method for providing optimal estimation of real-time vehicle distance along a route such as, but not limited to a train track, and that is robust to errors and disturbances that are likely to be encountered in the specific route, i.e. railroad environment in order to be safely deployed and to ensure the distance estimation is accurate.